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dc.contributor.advisorGrobbelaar, J. U.
dc.contributor.authorMohale, Lineo Rose
dc.date.accessioned2016-01-14T07:19:15Z
dc.date.available2016-01-14T07:19:15Z
dc.date.copyright2011-01
dc.date.issued2011-01
dc.date.submitted2011-01
dc.identifier.urihttp://hdl.handle.net/11660/2208
dc.description.abstractEnglish: The occurrence of cyanobacterial blooms that may be toxic is one of the major consequences of eutrophication. The prevalence of cyanobacteria and their toxins in reservoirs create a significant water quality problem and complicates the water purification process for producing safe drinking water. Microcystin is the dominant group of cyanotoxins and the most commonly occurring variant is microcystin-LR. The purpose of this study was to determine the presence of cyanotoxins in the reservoirs and drinking water supplied to the city and towns of Bloemfontein, Thaba Nchu and Botshabelo, in the central region of South Africa. To achieve this, the microcystin-LR concentrations were determined in Rustfontein, Mockes and Maselspoort Dams and the efficiency of treatment processes at Rustfontein and Maselspoort treatment plants in removing this cyanotoxin were investigated. In situ measurements of electrical conductivity (EC), dissolved oxygen (DO), pH and surface water temperature were done at two-weekly intervals over the study period. Water samples were collected and analysed upon return to the laboratory for NO3-N, PO4-P, chlorophyll-a, dominant algal species and microcystin-LR. Final treated water from Rustfontein and Maselspoort water treatment facilities was also analysed for microcystin-LR. Physico-chemical variables displayed no clear-cut seasonal trends except for surface water temperature which followed a distinctive seasonal pattern with lower values in winter and higher values in summer. The concentration of DO seemed to be influenced by water temperature, photosynthetic activity of phytoplankton, wind induced mixing and decomposition of organic matter. Based on the nutrient content, these impoundments were found to be eutrophic. However, in terms of chlorophyll-a concentrations, Maselspoort Dam was mesotrophic, Rustfontein Dam eutrophic and Mockes Dam hypertrophic. Cyanobacteria genera that were commonly found in the three impoundments were Microcystis, Anabaena and Oscillatoria. Oscillatoria was occasionally dominant in Mockes Dam with Ceratium as co-dominant. Microcystis was occasionally dominant in Rustfontein Dam. Euglenoids such as Euglena, Trachelomonas and Phacus, that are indicative of presence of organic matter, were occasionally present, especially in Mockes and Maselspoort Dams. There were no severe cyanobacterial blooms during the study period except for a single bloom of Microcystis in Rustfontein in April 2010. This explains why the concentrations of microcystin-LR or microcystin-LR equivalents in the three impoundments were generally low or undetectable. The highest concentration measured was 1.19 μg/L and this was in Rustfontein Dam during the bloom. Microcystin-LR was never detected in the final treated water from Rustfontein but was detected once in treated water from Maselspoort (0.043 μg/L). This is lower than the 1 μg/L proposed by WHO as an acceptable level of microcystin-LR or microcystin-LR equivalents in drinking water. Based on these results it was concluded that the treatment processes at both facilities were relatively efficient in removing microcystin-LR and that the water supplied to Bloemfontein, Botshabelo and Thaba Nchu is indeed safe. However, it is believed that the efficiency of these treatment processes might be compromised when high concentrations of microcystin-LR or microcystin-LR equivalents occur in source waters. Rustfontein Dam seemed to have the potential to develop massive cyanobacterial blooms and this could result in occurrence of high concentrations of microcystin-LR or microcystin-LR equivalents in the water. It is, therefore, recommended that the water treatment facilities at Rustfontein and Maselspoort should consider introducing more advanced treatments such as an activated carbon polishing step. It is also recommended that cyanotoxin analysis should be part of routine water quality monitoring.en_ZA
dc.description.abstractAfrikaans: Die voorkoms van sianobakteriële opbloeie wat moontlik toksies kan wees, is een van die gevolge van eutrofikasie. Sianobakterieë en hulle toksiene is „n probleem in opgaardamme en bemoeilik die suiwering van water, asook die voorsiening van drinkwater. Mikrosistien is die groep sianotoksiene wat die meeste voorkom en mikrosistien-LR domineer hierdie groep toksiene. Die doel van die studie was om die voorkoms van sianotoksiene in die opgaardamme en drinkwater van die stad Bloemfontein en dorpe Thaba Nchu en Botshabelo in sentraal Suid-Afrika te ondersoek. Om dit te doen is die konsentrasies mikrosistien-LR in Rustfontein-, Mockes- en Maselspoortdamme bepaal, asook in die gesuiwerde water van die Rustfontein en Maselspoort suiweringsaanlegte. In situ metings van konduktiwiteit (EC), opgeloste suurstof (DO), pH en oppervlak temperature is tweeweekliks gedurende die studietydperk gedoen. Watermonsters is versamel en na terugkeer in die laboratorium geanaliseer vir NO3-N, PO4-P, chlorofil-a, dominante alg spesies en mikrosistien-LR. Finaal gesuiwerde water van Rustfontein en Maselspoort suiweringsaanlegte is vir mikrosistien-LR getoets. Geen duidelike seisoenale patroon was herkenbaar in die fisies-chemiese resultate nie, behalwe vir watertemperatuur wat duidelik laer in die winter en hoër in die somer was. DO was duidelik beïnvloed deur watertemperatuur, fotosintetiese aktiwiteit van die fitoplankton, windvermenging en die ontbinding van organiese materiaal. Volgens die voedingstofkonsentrasies kan die opgaardamme as eutrofies geklassifiseer word. In terme van die chlorofil-a konsentrasies is Maselspoortdam mesotrofies, Rustfonteindam eutrofies en Mockesdam hipereutrofies. Die dominante sianobakteriese genera in die opgaardamme was Microcystis, Anabaena en Oscillatoria. Oscillatoria was met tye dominant in Mockersdam gevolg deur Ceratium. Microcystis was met tye dominant in Rustfonteindam. Euglenoiede soos Euglena, Trachelomonas en Phacus, wat op die teenwoordigheid organiese materiaal kan dui, is met tye in Mockesdam en Maselspoortdam waargeneem. Geen uitsonderlike opbloeie van sianobakterieë het gedurende die studietydperk voorgekom nie, behalwe vir 'n Microcystis opbloei in April 2010 in Rustfonteindam. Dit verduidelik waarom die konsentrasies van mikrosistien of hulle derivate laag of onmeetbaar in die drie opgaardamme was. Die hoogste konsentrasie van 1.19 μg/L is in Rustfonteindam gedurende die opbloei gemeet. Mikrosistien-LR was nooit in die gesuiwerde water van die Rustfonteinaanleg gemeet nie, maar wel een keer in die behandelde water van Maselpoortsuiweringsaanleg (0.043 μg/L). Dit is heelwat laer as die 1 μg/L riglyn soos deur die Wêreld Gesondheidsorganisasie (WHO) voorgestel vir mikrosistien-LR en derivate in drinkwater. Hiervolgens kon afgelei word dat die suiweringsaanlegte relatief effektief is om mikrosistien-LR in die water wat aan Bloemfontein, Thaba Nchu en Botshabelo voorsien word, te verwyder. Dit word egter voorsien dat die suiwering onvoldoende sal wees indien hoë konsentrasies mikrosistien-LR in die rou water sou voorkom. Die moontlikheid bestaan dat groot opbloeie in Rustfonteindam sou kan voorkom wat weer tot hoë mikrosistienkonsentrasies in die rou water sou kon lei. Dit word voorgestel dat die suiweringsaanlegte gevorderde stappe soos 'n geaktiveerde koolstof stap insluit. Verder word voorgestel dat daar vir sianotoksiene op 'n roetine grondslag geanaliseer word.af
dc.description.sponsorshipUniversity of the Free State, Strategic Cluster, Water Management in Water-Scarce Areasen_ZA
dc.description.sponsorshipGovernment of Lesothoen_ZA
dc.language.isoenen_ZA
dc.publisherUniversity of the Free Stateen_ZA
dc.subjectDissertation (M.Sc. (Plant Sciences))--University of the Free State, 2011en_ZA
dc.subjectWater-purification -- South Africa -- Bloemfonteinen_ZA
dc.subjectWater quality management -- South Africa -- Bloemfonteinen_ZA
dc.subjectWater quality -- Bloemfontein -- South Africaen_ZA
dc.subjectEutrophicationen_ZA
dc.subjectCynobacterial bloomsen_ZA
dc.subjectMockes Damen_ZA
dc.subjectMaselspoort Damen_ZA
dc.subjectRustfontein Damen_ZA
dc.subjectTreatment processesen_ZA
dc.subjectSafe drinking wateren_ZA
dc.subjectMicrocystin-LRen_ZA
dc.titleImpact of cyanobacterial toxins on water quality and supplyen_ZA
dc.typeDissertationen_ZA
dc.rights.holderUniversity of the Free Stateen_ZA


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